Transformer VA, kVA, MVA Calculator, Rating Calculation Formula

Transformer VA, kVA, MVA calculator:

Enter the voltage or current or VA rating of the transformer to calculate the raminaing one.

Resistance (R):
Current (I):
Voltage (V):
Rating (S):


Transformer VA, kVA, MVA calculation:

Transformers are static equipment which is used to convert the voltage or current to the different levels. It is a heart of power systems. The total deliverable apparent power is the rating of the transformer. The unit of apparent power is VA (Volt-Amp). Hence the transformer is rated by the VA only.

Sometimes the transformer can be rated by kVA (kilo Volt-Amps) or MVA (Mega Volt-Amp). Here kVA and MVA are the larger units which are used to indicate the bigger size of the transformer.

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How to calculate VA, kVA and MVA rating of the transformer?

As we said VA is the unit of apparent power and it will be calculated by the product of input voltage and input current or the product of output voltage and output current.

In a transformer, we have two voltages and two currents and they are V(primary) Primary voltage in Volts, V(secondary) Secondary voltage in Volts, I(Primary) Primary current in Amps and I(secondary) secondary current in Amps.

VA rating calculation formula:

Transformer Rating in VA for single phase

S(VA)= V(primary) * I(Primary) = V(secondary) * I(secondary)

It is the product of the primary voltage and primary current or secondary voltage and secondary current. It does not depend on the power factor.

Transformer Rating in VA for three-phase

The three-phase concern we have two formula based on the line to line and line to phase voltage and they are,

Based on Line voltage

S(VA)= V(primary L-L) * I(Primary) = V(secondary L-L) * I(secondary)

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Based on Neutral Voltage,

S(VA)= 1.732 * V(primary L-N) * I(Primary) = 1.732 * V(secondary L-N) * I(secondary)


Calculate the VA rating of the single-phase transformer whose primary voltage is 230 and primary rated current is 10 Amps.

VA = 230 * 10

Transformer rating = 2300VA

Also, it can be calculated from the secondary voltage and current.

kVA rating calculation formula:

kVA rating of the transformer S(kVA) is equal to the product of primary current I(Primary) in amps and Primary voltage V(primary) in volts divided by 1000.

S(kVA) = V(primary) * I(Primary) / 1000 = V(secondary) * I(secondary) / 1000

For three phase transformer kVA Calculations formula,

S(kVA)= 1.732 * V(primary L-N) * I(Primary) / 103 = √3 * V(secondary L-N) * I(secondary) / 103

S(kVA)= V(primary L-L) * I(Primary) / 103 = V(secondary L-L) * I(secondary) / 103


Calculate the kVA rating of the transformer whose secondary voltage of 11000 V and secondary current of 2Amps.

Apply our formula,

S(kVA) = 11000 * 2 / 1000 = 22 kVA

The transformer rating is 22kVA

MVA rating calculation formula:

MVA (Mega Volt-Amp) rating of the transformer S(MVA) is equal to the product of primary current I(Primary) in amps and Primary Voltage V(primary) in volts divided by 1000000.

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S(MVA) = V(primary) * I(Primary) / 1000000 = V(secondary) * I(secondary) / 1000000

Three phase transformer MVA calculations:

S(MVA)= 1.732 * V(primary L-N) * I(Primary) / 106 = √3 * V(secondary L-N) * I(secondary) / 106

S(MVA)= V(primary L-L) * I(Primary) / 106 = V(secondary L-L) * I(secondary) / 106


Calculate the MVA rating of the transformer whose primary voltage of 110000 V and secondary current of 100 Amps.

Apply our formula,

S(kVA) = 110000 * 100 / 1000000 = 11 MVA

The transformer rating is 11 MVA

For measuring current and voltage of the kVA and MVA rating we use a potential transformer and current transformer.

Calculate the transformer rating from Watts:

Watt is the unit of the real power P(W). VA rating of the transformer is equal to real power P(W) divided by power factor.

S(VA) = P(W) x pf

kVA rating from W,

S(kVA) = P(W) x pf / 1000

MVA rating from W,

S(MVA) = P(W) x pf / 1000000

In the same way for kVA and MVA from real power,

S(kVA) = P(kW) / pf

S(MVA) = P(MW) / pf

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Let we take and example, calculate the VA rating of the transformer output power 15000 W with the power factor of 0.90.

S(VA) = 15000 x 0.9 = 13500 VA

S(kVA) = 15000 x 0.9 /1000 = 13.5 kVA

S(MVA) = 15000 x 0.9 /1000000 = 0.0135 MVA



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